Portable abrading and polishing machine



March 14, 1933. T. F. BRACKETT PORTABLE ABRADING AND POLISHING MACHINEFiled Aug. 28, 1931 Patented Mar. 14, 1933 UNITED STATES TRACY F.BRACKETT, OF HIGHLAND PARK, MICHIGAN i ormuuarm ABRADING AND' roLIsHING1vIn`e1zt11vr'.'A

Application filed August 2 8, 1931'. Serial .No.`559,99`3.

My invention yrelates to improvements in portable sanding andpolishingmachines.

One `of the objects of my inventionisvto provide a portable machinewhich is par- 5 ticularly adaptable for operating on curved or irregularsurfaces.

A further object is to provide a portable machine having an abrading orpolishingY member which when applied tothe surface to ber treated, willconform itself tocurves or irregularities in the surface sov as to vhavea much greater area of uniform contact with the work than( is possiblewith the usual abrading and polishing Wheels.

Other objects of my invention will apf-` pear hereinafter.

Referring to the accompanying drawing Fig.v 1 is a viewl in elevationofa portable abrading and polishing machine embodying my invention; Fig.2 is a sectional view on the line 2-2 of Fig. l; l

Figs. 3, 4 and 5 are detail sectional views ofdifferent forms ofabradingand polishing elements which can be used inconnection with myinvention.

The usual abrading andi polishing wheels which are in common use are, ofcourse` cir-V cular'in shape having only a very limited which is beingtreated, and the treating of an extended surface or aV surface greaterthan the area of contact is accomplishedby moving the work and the wheelrelatively to each other. This area of contact is very limited evenlthough wheels are made flexible or yielding. This is particularly truein treating curved or irregular surfaces. The usual wheel cannot reachall portions of these surfaces and the pressure is. notuniformthroughout the areai'of' contact, making it very diiiicult to grind orpolish the Work uniformly.

I propose to employ a flexible beltv or band having an abrading surface'and maintained in'state of slackness or looseness whereby it will7 whenplaced' in contact with the work, adapt itself' to the curves orirregularities in the surface by conforming to the contour thereof. Iaccomplish this 'lby'usingf an' endiarea of Contact with the surface'ofthe work less` slack belt or band and. propelling this belt in 'the'line of itself in such manner that the; centrifugal force.v developedforces the belt the working surface of the'bel't against a1 considerableportion. of 'the' area' of` the 5 5 surface ofthe work.

y In the present lstructure a. suitable frame 1 Vis provided whichsupports the shafts 2' ofbelt'supp'orting'pulleys Sandwhich alsoservesasa suitable enclosure or housing for the driving chain 4 andsprocket wheels 7. The housing is. made iny two-sections, Fig. 2, whichare joined togetherl around their periphery by the bolts 5 so thataccess mayy be obtained to'the interior' of the housing 65" whendesired. The pulley y. shafts 2; are mounted in suitable bearings 6formed in the `frame housing and each shaft has a sprocket-'wheel 7 forther drive chain. Between the pulley shafts a suitable' electric 70driving motor 8 is mounted. The motor hasV i a 'shaft 9fextendingthrough a suitable opening in the wall of the housingy having at its enda pinion 10 in driving'engagementwith the chain, Fig.` 1.y Thisv drivesthe pulley shafts 2finthe samewdirection at the same speedy because thesprockets 7 are of ther samef size. The rear wallv of the housing hasupwardly and downwardly extending flanges: 11 with vvertical slots 12therein, and 80 screwsy 13 are passed through these slots and into themotor" .shell for clamping the motor shell: tothe frame. yThe slots 12per mit the motor and its pinion 10=to-be adjusted relatively to theframe' for the pur- 85' pose ofadjusting the tension on the drive chain.Themotorishell has a downwardlyv extending. flangel which conforms tothelowerflange 11 of the frame housing to pro-V vide forVv the lowerclamping screw 13. While I- have shown` 'an' electric *motori attachedtothe frame for drilving'the pulleys, it is obvious that a flexible.shaft may be used. The shaft may be attached tothe frame and connected'to the pinion 10v for 95 driving-J the chain. e

The structure shown is'intended as a portf able unit and is providedwith suitable handles l5' for the operator.` OneA of these handlesisplaced in alignment with each No Aslipping laterally off of the pulleys.

' purpose.

The pulley shafts 2 and the pulleysV mounted thereon extendsconsiderably beyond the frame a sufficient distance so that' theframewill not interfere with the manipulation of the abradingbelt inrall directionsvwith'respect to the'work. VThe .beltV pulleys 3 areyspaced apartto provide space between them for the work'. rllhe pulleyshave flanges 8 to prevent the belt from The belt A is endless andextends around. both pulleys to provide driving contactV with the gulles.k lhe length of the belt is Greater. I :v ,a L o 'than it would be 1rstretched tightaround the pulleys so that the reaches or Vunsupy portedportions A can bow outwardly under Y the action of centrifugal forcedeveloped when'the belt is driven vwhen the working portion of thelowerY reach A is placed in ContactV with the surface ofv work to betreated, its flexibility permits ittoconform tothe surface of the work,this conformance being brought about by the centrifugal force developedin the belt. In Fig. l` an irregular curved surface is indicated by thedotted line B, and the manner in which the vbelt conforms to its surfaceis indicated by the dotted lines A. f

rlhe belt may be made up of several narrowfsections placed side by sideor it may be a single piece of the proper width for the purpose. rlheabrasive or polishing, material may be applied directly to the outersurface of the belt or it may be carried on a separate stripl?, Figs. 3,l and 5 and the strip 17 applied to the outer surface of the belt bystitching or any other well known method of applying abrasives topolishing implements.

Figs. 8, 1- and 5 indicate several .different types ofv abrasives. usedin abrading Aand polishing work. In Fig. 3 the abrasive is lshown as awire pile 18 on the fabric strip 17. ln Fig. fthe polishing surfaceshown has cloth polishing pads or loops 19 stitched at intervals 2O tothe strip 17. kFigo shows the abrasive, such as emery or carborundum 21,applied to the strip 17. Y

In a portable uni" of this character ythe operator has almost universalmovement lof the unit in placing the belt in contact with the work, and,due to the slackness and flexibilityof the belt it will readily adaptitself to this universal movement and conform itself to the curvesorirregularities of the surface which is being treated. The slack belt hasa comparatively great area of contact with the surface being treated andthe pressure on this surface will be practically uniform throughout thearea thereof with the result much more uniform and efficient work can beperformed at a much greater speed. Y

I am aware that changes and alterations may be made in the constructionand arf housing, sprocketsfast on said shafts in said housing, anendless chain directed about said sprockets, mounting means on saidhousing intermediate said bearings, a driving motor, a sprocket on theshaft of'thermotor and meshed with saidA chain, means adjustablysecuring said motor on said mounting means whereby said motor maybemoved to tension said chain, said motor driving said chain to impartrotative-movement to vsaid shafts, flanged pulleys fast on the portionsof said shafts extending beyondsaid hous-V ing, and an endless flexiblebelt directed about said pulleys and of greater length than required tobe stretched tautaround the pulleys, said belthaving an abrading surfaceon the outer face thereof, said rbelt being bowed outwardlyby thecentrifugal force developed during movement. imparted to the beltwhereby the abrading surface on the bowed portion of the belt may beengaged with and conformed to a surface to be abraded. Y

2. In a device of the *Y class described-,a housing having fixedbearings therein, shafts journaled insaid bearings and disposed inspaced relation andextending beyond said housing, sprockets fast on saidshafts in said housing, an endless chain directedabout said sprockets,mounting means on said housing intermediate said bearings, a drivingmotor, a sprocket on the shaft of the ,motor and meshed with said chain,flanges on said housing intermediate said bearings and extendingtransversely of the housing,` a Si' bracket kon the motor, meansadjustably securing said bracket to said flanges to vary the position ofsaid motor andthe sprocket on the shaft thereof to tension said chain,

said motor driving said chain to impart roii" tative movement to saidshafts, anged pulleys fast on the portions of said shaftsextendingibeyond said housing, an endless flexible belt directed aboutsaid pulleys'and of greater lengthV vthan required to ybe stretched tautaround the pulleys, said belt having an abrading surface on the outerface thereof7 handles on said housing extending therefrom in alignmentWith said shafts, said handles being grasped to permit movement of saidhousing whereby a portion of the belt intermediate the pulleys bowedout- Wardly by the centrifugal force developed during movement impartedto the belt may be engaged With and conformed to a surface to beabraded.

TRACY F. BRACKETT.

